This invention relates generally to magnetically operated valves and more particularly concerns a valve having a rotatable closure element which is rotated between open and closed positions by an electromagnet. The rotary magnetic valve is applicable to many uses and is particularly useful in dual evaporator refrigeration systems.
Energy efficiency is an extremely important factor in the design of refrigeration systems. This is particularly so for household refrigerators having multiple temperature requirements, e.g., fresh food and freezer compartments. The refrigeration cycle traditionally used in household refrigerators utilizes a single evaporator operated at the low freezer temperature. Refrigerator air is blown across the evaporator and the air flow is split so that a large part of the flow goes to the freezer compartment and the remainder goes to the fresh food compartment. This cycle thus produces a refrigeration effect which is appropriate for the freezer compartment but lower than need be for the fresh food compartment. As such, the traditional cycle is not as energy efficient as a cycle having two evaporators operating at different temperatures.
Thus, one cost effective approach to better energy efficiency has been the development of more efficient refrigeration cycles. For example, the above-mentioned U.S. Pat. No. 5,228,308 discloses an efficient dual evaporator, single compressor refrigeration cycle. U.S. Pat. No. 4,242,116 to Matthias Aschberger et al discloses another dual evaporator, single compressor cycle. Both of these cycles require a valving arrangement for selectively controlling the flow of refrigerant through the system.
Conventional solenoid valves will satisfy the flow control requirements but tend to operate at excessive noise and wear levels. For instance, U.S. Pat. No. 4,242,116 discloses a three-way magnetic valve which comprises a tubular housing having an axial bore hole with an inlet to the bore hole and an outlet at each end of the housing. A plunger-armature assembly is disposed in the bore hole and is moved longitudinally against a spring force by an electromagnet. Sealing cones on the ends of the plunger engage valve seats at the respective outlets for selectively closing the outlets. The action of the sealing cones striking the respective valve seats each time the plunger position is switched produces a relatively loud clicking noise and significant part wear. For these refrigeration cycles, it is estimated that a valve will need a 20 million cycle life.
Generally, it is important to make the sealing cones as small as possible because the noise they create increases as their weight increases. In addition, more energy will be required to move heavier sealing cones. Because the sealing cones must be small, the cross-sectional area of the outlet orifices is limited. In applications where a pressure drop is not desired, particularly for vapor phase flow, the orifice size limitation can be troublesome because as the orifice size is reduced, the pressure drop increases.
Accordingly, there is a need for a valve suitable for use in refrigeration systems which operates virtually silently and without substantial wear. There is an additional need for a valve in which the orifice size is not unduly limited, thereby avoiding unnecessary pressure drops.